EP2131246B1

EP2131246B1 - Toner compositions

Info

Publication number: EP2131246B1
Application number: EP09160560.0A
Authority: EP
Inventors: Ke Zhou; Maria N.V. Mcdougall; Edward G. Zwartz; Karen A. Moffat; Paul J. Gerroir
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 2008-06-06
Filing date: 2009-05-19
Publication date: 2016-03-30
Anticipated expiration: 2029-05-19
Also published as: JP5448583B2; US8084180B2; JP2009294655A; CN101598912B; BRPI0901995A2; MX2009005789A; CN101598912A; KR101489698B1; EP2131246A1; KR20090127229A; US20090305159A1

Description

The present disclosure relates to toners suitable for electrophotographic apparatuses.
Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. These toners may be formed by aggregating a colorant with a latex polymer formed by emulsion polymerization. For example, U.S. Patent No. 5,853,943 is directed to a semi-continuous emulsion polymerization process for preparing a latex by first forming a seed polymer.
Polyester EA ultra low melt (ULM) toners have been prepared utilizing amorphous and crystalline polyester resins. Some of these toners have poor charging characteristics, which may be due to the crystalline resin component migrating to the surface during coalescence. The amorphous resin may also be plasticized by the crystalline resin, which may result in poor blocking. A core-shell approach, wherein a shell including a linear amorphous resin may be added to encapsulate the crystalline-amorphous composite has been attempted; however, charging and blocking still needs to be improved.
US-A-2006/292477 discloses a toner comprising a binder resin containing a coloring agent, a crystalline resin and an amorphous resin. The experimental part of this publication discloses toner particles having a core-shell structure, wherein the core comprises a crystalline resin and an amorphous resin, and the shell comprises an amorphous polyester resin having a weight average molecular weight of 10,400, 11,500 or 12,600.
US-A-2006/216628 discloses toner particles having a core-shell structure, wherein the core contains a crystalline resin and an amorphous resin, and the shell comprises an amorphous styrene-acrylate polymer having a weight average molecular weight of 15,000.
US-A-2007/048647 discloses a toner having a core-shell structure, wherein the core contains a colorant, an amorphous resin and a block polymer comprising a crystalline part and an amorphous part. The shell resin prepared in the experimental part of this publication is an amorphous polyester having a weight average molecular weight of 12,300.
The present invention provides a toner composition comprising toner particles comprising:

a core comprising at least one crystalline resin, and one or more optional ingredients selected from the group consisting of colorants, optional waxes, and combinations thereof; and
a shell comprising a high molecular weight amorphous polyester resin having a weight average molecular weight of from 20,000 to 1,000,000, as determined by Gel Permeation Chromatography using polystyrene standards,
wherein the high molecular weight amorphous polyester resin comprises a poly(propoxylated bisphenol A co-fumarate) of the following formula:
wherein m is from 10 to 5000, and wherein the high molecular weight amorphous polyester resin is present in an amount of from 20 to 100 percent by weight of the shell resin, has a glass transition temperature of from 40 to 100 °C, a softening point of from 100 to 200 °C, and a melt viscosity of from 50 to 1,000,000 Pa·s at 130°C.

Preferred embodiments of the present invention are set forth in the sub-claims.
The Figure is a graph depicting the differences in the rheological properties of a toner produced with a resin of the present disclosure compared with a toner produced with a control resin.
The present disclosure provides toner particles having excellent charging properties. The toner particles possess a core-shell configuration, with a high molecular weight amorphous polyester resin in the shell. The glass transition temperature (Tg) of toner particles of the present disclosure is higher than toner particles possessing low molecular weight amorphous resins in the shell.
Toner particles of the present disclosure have improved toner blocking.

Core Resins

Any latex resin may be utilized in forming a toner core of the present disclosure. Such resins, in turn, may be made of any suitable monomer. Suitable monomers useful in forming the resin include styrenes, acrylates, methacrylates, butadienes, isoprenes, acrylic acids, methacrylic acids, acrylonitriles, diol, diacid, diamine, diester, and mixtures thereof. Any monomer employed may be selected depending upon the particular polymer to be utilized.
In embodiments, the polymer utilized to form the resin core may be a polyester resin, including the resins described in U.S. Patent Nos. 6,593,049 and 6,756,176 . Suitable resins may also include a mixture of an amorphous polyester resin and a crystalline polyester resin as described in U.S. Patent No. 6,830,860 . In embodiments, the resin may be formed by emulsion polymerization methods.
In embodiments, the resin may be a polyester resin formed by reacting a diol with a diacid in the presence of an optional catalyst. For forming a crystalline polyester, suitable organic diols include aliphatic diols with from 2 to 36 carbon atoms, such as 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, pentylene glycol, 1,6-hexanediol, hexylene glycol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, neopentyl glycol, ethylene glycol, diethylene glycol, dipropylene glycol and combinations thereof; alkali sulfo-aliphatic diols such as sodio 2-sulfo-1,2-ethanediol, lithio 2-sulfo-1,2-ethanediol, potassio 2-sulfo-1,2-ethanediol, sodio 2-sulfo-1,3-propanediol, lithio 2-sulfo-1,3-propanediol, potassio 2-sulfo-1,3-propanediol, and mixture thereof. The aliphatic and or aromatic diol may be, for example, selected in an amount of from 40 to 60 mole percent, in embodiments from 42 to 55 mole percent, in embodiments from 45 to 53 mole percent, and the alkali sulfo-aliphatic diol can be selected in an amount of from 0 to 10 mole percent, in embodiments from 1 to 4 mole percent of the resin.
Examples of organic diacids or diesters selected for the preparation of the crystalline resins include oxalic acid, succinic acid, glutaric acid, adipic acid, succinic acid, suberic acid, 2-ethyl succinic acid, fumaric acid, maleic acid, maleic anhydride, dodecanedioic acid, dodecylsuccinic acid, 2-methyladipic acid, pimelic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, cyclohexane dicarboxylic acid, malonic acid and mesaconic acid, itaconic acid, 2-methylitaconic acid a diester or anhydride thereof, and combinations thereof; and an alkali sulfo-organic diacid such as the sodio, lithio or potassio salt of dimethyl-5-sulfo-isophthalate, dialkyl-5-sulfo-isophthalate-4-sulfo-1,8-naphthalic anhydride, 4-sulfo-phthalic acid, dimethyl-4-sulfo-phthalate, dialkyl-4-sulfo-phthalate, 4-sulfophenyl-3,5-dicarbomethoxybenzene, 6-sulfo-2-naphthyl-3,5-dicarbomethoxybenzene, sulfo-terephthalic acid, dimethyl-sulfo-terephthalate, 5-sulfo-isophthalic acid, dialkyl-sulfo-terephthalate, sulfoethanediol, 2-sulfopropanediol, 2-sulfobutanediol, 3-sulfopentanediol, 2-sulfohexanediol, 3-sulfo-2-methylpentanediol, 2-sulfo-3,3-dimethylpentanediol, sulfo-p-hydroxybenzoic acid, N,N-bis(2-hydroxyethyl)-2-amino ethane sulfonate, or mixtures thereof. The organic diacid may be selected in an amount of, for example, in embodiments from 40 to 60 mole percent, in embodiments from 42 to 52 mole percent, in embodiments from 45 to 50 mole percent, and the alkali sulfo-aliphatic diacid can be selected in an amount of from 1 to 10 mole percent of the resin.
Examples of crystalline resins include polyesters, polyamides, polyimides, polyolefins, polyethylene, polybutylene, polyisobutyrate, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, polypropylene, and mixtures thereof. Specific crystalline resins may be polyester based, such as poly(ethylene-adipate), poly(propylene-adipate), poly(butylene-adipate), poly(pentylene-adipate), poly(hexylene-adipate), poly(octylene-adipate), poly(ethylene-succinate), poly(propylene-succinate), poly(butylene-succinate), poly(pentylene-succinate), poly(hexylene-succinate), poly(octylene-succinate), poly(ethylene-sebacate), poly(propylene-sebacate), poly(butylene-sebacate), poly(pentylene-sebacate), poly(hexylene-sebacate), poly(octylene-sebacate), alkali copoly(5-sulfoisophthaloyl)-copoly(ethylene-adipate), alkali copoly(5-sulfoisophthaloyl)-copoly(propylene-adipate), alkali copoly(5-sulfoisophthaloyl)-copoly(butylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(pentylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(hexylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(octylene-adipate), alkali copoly(5-sulfoisophthaloyl)-copoly(ethylene-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(propylene-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(butylenes-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(pentylene-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(hexylene-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(octylene-succinate), alkali copoly(5-sulfo-isophthaloyl)-copoly(ethylene-sebacate), alkali copoly(5-sulfoisophthaloyl)-copoly(propylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(butylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(pentylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(hexylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(octylene-sebacate), wherein alkali is a metal like sodium, lithium or potassium. Examples of polyamides include poly(ethylene-adipamide), poly(propylene-adipamide), poly(butylenes-adipamide), poly(pentylene-adipamide), poly(hexylene-adipamide), poly(octylene-adipamide), poly(ethylene-succinamide), and poly(propylene-sebecamide). Examples of polyimides include poly(ethylene-adipimide), poly(propylene-adipimide), poly(butylene-adipimide), poly(pentylene-adipimide), poly(hexylene-adipimide), poly(octylene-adipimide), poly(ethylene-succinimide), poly(propylene-succinimide), and poly(butylene-succinimide).
The crystalline resin may be present, for example, in an amount of from 5 to 50 percent by weight of the toner components, in embodiments from 5 to 35 percent by weight of the toner components. The crystalline resin can possess various melting points of, for example, from 30° C to 120° C, in embodiments from 50° C to 90° C. The crystalline resin may have a number average molecular weight (M_n), as measured by gel permeation chromatography (GPC) of, for example, from 1,000 to 50,000, in embodiments from 2,000 to 25,000, and a weight average molecular weight (M_w) of, for example, from 2,000 to 100,000, in embodiments froml 3,000 to 80,000, as determined by Gel Permeation Chromatography using polystyrene standards. The molecular weight distribution (M_w/M_n) of the crystalline resin may be, for example, from 2 to 6, in embodiments from 2 to 4.
Examples of diacid or diesters selected for the preparation of amorphous polyesters include dicarboxylic acids or diesters such as terephthalic acid, phthalic acid, isophthalic acid, fumaric acid, maleic acid, maleic anhydride, succinic acid, malonic acid, itaconic acid, 2-methylitaconic acid, 2-ethyl succinic acid, succinic anhydride, dodecylsuccinic acid, 2-methyladipic acid, dodecylsuccinic anhydride, glutaric acid, glutaric anhydride, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimethyl terephthalate, diethyl terephthalate, dimethylisophthalate, diethylisophthalate, dimethylphthalate, phthalic anhydride, diethylphthalate, dimethylsuccinate, dimethylfumarate, dimethylmaleate, dimethylglutarate, dimethyladipate, dimethyl dodecylsuccinate, and combinations thereof. The organic diacid or diester may be present, for example, in an amount from 40 to 60 mole percent of the resin, in embodiments from 42 to 55 mole percent of the resin, in embodiments from 45 to 53 mole percent of the resin.
Examples of diols utilized in generating the amorphous polyester include 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, 2,2-dimethylpropanediol, 2,2,3-trimethylhexanediol, heptanediol, dodecanediol, bis(hydroxyethyl)-bisphenol A, bis(2-hydroxypropyl)-bisphenol A, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, xylenedimethanol, cyclohexanediol, diethylene glycol, bis(2-hydroxyethyl) oxide, dipropylene glycol, dibutylene, and combinations thereof. The amount of organic diol selected can vary, and may be present, for example, in an amount from 40 to 60 mole percent of the resin, in embodiments from 42 to 55 mole percent of the resin, in embodiments from 45 to 53 mole percent of the resin.
Polycondensation catalysts which may be utilized for either the crystalline or amorphous polyesters include tetraalkyl titanates, dialkyltin oxides such as dibutyltin oxide, tetraalkyltins such as dibutyltin dilaurate, and dialkyltin oxide hydroxides such as butyltin oxide hydroxide, aluminum alkoxides, alkyl zinc, dialkyl zinc, zinc oxide, stannous oxide, or combinations thereof. Such catalysts may be utilized in amounts of, for example, from 0.01 mole percent to 5 mole percent based on the starting diacid or diester used to generate the polyester resin.
In embodiments, suitable amorphous resins include polyesters, polyamides, polyimides, polyolefins, polyethylene, polybutylene, polyisobutyrate, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, polypropylene, and combinations thereof. Examples of amorphous resins which may be utilized include poly(styrene-acrylate) resins, crosslinked, for example, from 10 percent to 70 percent, poly(styrene-acrylate) resins, poly(styrene-methacrylate) resins, crosslinked poly(styrene-methacrylate) resins, poly(styrene-butadiene) resins, crosslinked poly(styrene-butadiene) resins, alkali sulfonated-polyester resins, branched alkali sulfonated-polyester resins, alkali sulfonated-polyimide resins, branched alkali sulfonated-polyimide resins, alkali sulfonated poly(styrene-acrylate) resins, crosslinked alkali sulfonated poly(styrene-acrylate) resins, poly(styrene-methacrylate) resins, crosslinked alkali sulfonated-poly(styrene-methacrylate) resins, alkali sulfonated-poly(styrene-butadiene) resins, and crosslinked alkali sulfonated poly(styrene-butadiene) resins. Alkali sulfonated polyester resins may be useful in embodiments, such as the metal or alkali salts of copoly(ethylene-terephthalate)-copoly(ethylene-5-sulfo-isophthalate), copoly(propylene-terephthalate)-copoly(propylene-5-sulfo-isophthalate), copoly(diethylene-terephthalate)-copoly(diethylene-5-sulfo-isophthalate), copoly(propylene-diethylene-terephthalate)-copoly(propylene-diethylene-5-sulfoisophthalate), copoly(propylene-butylene-terephthalate)-copoly(propylene-butylene-5-sulfo -isophthalate), copoly(propoxylated bisphenol-A-fumarate)-copoly(propoxylated bisphenol A-5-sulfo-isophthalate), copoly(ethoxylated bisphenol-A-fumarate)-copoly(ethoxylated bisphenol-A-5-sulfo-isophthalate), and copoly(ethoxylated bisphenol-A-maleate)-copoly(ethoxylated bisphenol-A-5-sulfo-isophthalate), and wherein the alkali metal is, for example, a sodium, lithium or potassium ion.
Examples of other suitable latex resins or polymers which may be utilized include poly(styrene-butadiene), poly(methylstyrene-butadiene), poly(methyl methacrylate-butadiene), poly(ethyl methacrylate-butadiene), poly(propyl methacrylate-butadiene), poly(butyl methacrylate-butadiene), poly(methyl acrylate-butadiene), poly(ethyl acrylate-butadiene), poly(propyl acrylate-butadiene), poly(butyl acrylate-butadiene), poly(styrene-isoprene), poly(methylstyrene-isoprene), poly(methyl methacrylate-isoprene), poly(ethyl methacrylate-isoprene), poly(propyl methacrylate-isoprene), poly(butyl methacrylate-isoprene), poly(methyl acrylate-isoprene), poly(ethyl acrylate-isoprene), poly(propyl acrylate-isoprene), poly(butyl acrylate-isoprene); poly(styrene-propyl acrylate), poly(styrene-butyl acrylate), poly(styrene-butadiene-acrylic acid), poly(styrene-butadiene-methacrylic acid), poly(styrene-butadiene-acrylonitrile-acrylic acid), poly(styrene-butyl acrylate-acrylic acid), poly(styrene-butyl acrylate-methacrylic acid), poly(styrene-butyl acrylate-acrylonitrile), and poly(styrene-butyl acrylate-acrylonitrile-acrylic acid), and combinations thereof. The polymers may be block, random, or alternating copolymers.
In embodiments, an unsaturated polyester resin may be utilized as a latex resin. Examples of such resins include those disclosed in U.S. Patent No. 6,063,827 . Exemplary unsaturated polyester resins include poly(propoxylated bisphenol co-fumarate), poly(ethoxylated bisphenol co-fumarate), poly(butyloxylated bisphenol co-fumarate), poly(co-propoxylated bisphenol co-ethoxylated bisphenol co-fumarate), poly(1,2-propylene fumarate), poly(propoxylated bisphenol co-maleate), poly(ethoxylated bisphenol co-maleate), poly(butyloxylated bisphenol co-maleate), poly(co-propoxylated bisphenol co-ethoxylated bisphenol co-maleate), poly(1,2-propylene maleate), poly(propoxylated bisphenol co-itaconate), poly(ethoxylated bisphenol co-itaconate), poly(butyloxylated bisphenol co-itaconate), poly(co-propoxylated bisphenol co-ethoxylated bisphenol co-itaconate), poly(1,2-propylene itaconate), and combinations thereof.
In embodiments, a suitable amorphous polyester resin may be a poly(propoxylated bisphenol A co-fumarate) resin having the following formula (I):
wherein m may be from 5 to 1000.
An example of a linear propoxylated bisphenol A fumarate resin which may be utilized as a latex resin is available under the trade name SPARII from Resana S/A Industrias Quimicas, Sao Paulo Brazil. Other propoxylated bisphenol A fumarate resins that may be utilized and are commercially available include GTUF and FPESL-2 from Kao Corporation, Japan, and EM181635 from Reichhold, Research Triangle Park, North Carolina.
Suitable crystalline resins include those disclosed in U.S. Patent Application Publication No. 2006/0222991 . In embodiments, a suitable crystalline resin may include a resin composed of ethylene glycol and a mixture of dodecanedioic acid and fumaric acid comonomers with the following formula:
wherein b is from 5 to 2000 and d is from 5 to 2000.
The resins utilized to form the core may have a number average molecular weight (M_n) from 1000 to 1,000,000, in embodiments from 2000 to 500,000, and a weight average molecular weight (M_w) of from 2000 to 3,000,000, in embodiments from 4,000 to 1,500,000, as determined by Gel Permeation Chromatography (GPC) using polystyrene standards. For example, in embodiments, a poly(propoxylated bisphenol A co-fumarate) resin as described above may be utilized in the core. Such a polyester resin may have a weight average molecular weight (Mw) of from 2000 to 3,000,000, in embodiments from 4,000 to 1,500,000, and a number average molecular weight of from 1000 to 1,000,000, in embodiments from 2000 to 500,000, as determined by gel permeation chromatography (GPC).
In embodiments, the resin utilized in the core may have a glass transition temperature of from 35°C to 100°C, in embodiments from 40°C to 80°C. In further embodiments, the resin utilized in the core may have a melt viscosity of from 10 to 1,000,000 Pa*S at about 130°C, in embodiments from 20 to 100,000 Pa*S.
One, two, or more toner resins may be used. In embodiments where two or more toner resins are used, the toner resins may be in any suitable ratio (e.g., weight ratio) such as for instance about 10% (first resin)/90% (second resin) to about 90% (first resin)/10% (second resin).

Toner

The resin described above may be utilized to form toner compositions. Such toner compositions may include optional colorants, waxes, and other additives. Toners may be formed utilizing any method within the purview of those skilled in the art.

Surfactants

In embodiments, colorants, waxes, and other additives utilized to form toner compositions may be in dispersions including surfactants. Moreover, toner particles may be formed by emulsion aggregation methods where the resin and other components of the toner are placed in one or more surfactants, an emulsion is formed, toner particles are aggregated, coalesced, optionally washed and dried, and recovered.
One, two, or more surfactants may be utilized. The surfactants may be selected from ionic surfactants and nonionic surfactants. Anionic surfactants and cationic surfactants are encompassed by the term "ionic surfactants." In embodiments, the surfactant may be utilized so that it is present in an amount of from 0.01% to 5% by weight of the toner composition, for example from 0.75% to 4% by weight of the toner composition, in embodiments from 1% to 3% by weight of the toner composition.

Colorants

As the colorant to be added, various known suitable colorants, such as dyes, pigments, mixtures of dyes, mixtures of pigments, mixtures of dyes and pigments, may be included in the toner. The colorant may be included in the toner in an amount of, for example, 0.1 to 35 percent by weight of the toner, or from 1 to 15 weight percent of the toner, or from 3 to 10 percent by weight of the toner.

Wax

Optionally, a wax may also be combined with the resin and a colorant in forming toner particles. When included, the wax may be present in an amount of, for example, from 1 weight percent to 25 weight percent of the toner particles, in embodiments from 5 weight percent to 20 weight percent of the toner particles.
Waxes that may be selected include waxes having, for example, a weight average molecular weight of from 500 to 20,000, in embodiments from 1,000 to 10,000.

Toner Preparation

The toner particles may be prepared by any method within the purview of one skilled in the art. Although embodiments relating to toner particle production are described below with respect to emulsion-aggregation processes, any suitable method of preparing toner particles may be used, including chemical processes, such as suspension and encapsulation processes disclosed in U.S. Patent Nos. 5,290,654 and 5,302,486 . In embodiments, toner compositions and toner particles may be prepared by aggregation and coalescence processes in which small-size resin particles are aggregated to the appropriate toner particle size and then coalesced to achieve the final toner particle shape and morphology.
In embodiments, toner compositions may be prepared by emulsion-aggregation processes, such as a process that includes aggregating a mixture of an optional colorant, an optional wax and any other desired or required additives, and emulsions including the resins described above, optionally in surfactants as described above, and then coalescing the aggregate mixture. A mixture may be prepared by adding a colorant and optionally a wax or other materials, which may also be optionally in a dispersion(s) including a surfactant, to the emulsion, which may be a mixture of two or more emulsions containing the resin. The pH of the resulting mixture may be adjusted by an acid such as, for example, acetic acid or nitric acid. In embodiments, the pH of the mixture may be adjusted to from 4 to 5. Additionally, in embodiments, the mixture may be homogenized. If the mixture is homogenized, homogenization may be accomplished by mixing at 600 to 4,000 revolutions per minute. Homogenization may be accomplished by any suitable means, including, for example, an IKA ULTRA TURRAX T50 probe homogenizer.
Following the preparation of the above mixture, an aggregating agent may be added to the mixture. Any suitable aggregating agent may be utilized to form a toner. Suitable aggregating agents include, for example, aqueous solutions of a divalent cation or a multivalent cation material. The aggregating agent may be, for example, polyaluminum halides such as polyaluminum chloride (PAC), or the corresponding bromide, fluoride, or iodide, polyaluminum silicates such as polyaluminum sulfosilicate (PASS), and water soluble metal salts including aluminum chloride, aluminum nitrite, aluminum sulfate, potassium aluminum sulfate, calcium acetate, calcium chloride, calcium nitrite, calcium oxylate, calcium sulfate, magnesium acetate, magnesium nitrate, magnesium sulfate, zinc acetate, zinc nitrate, zinc sulfate, zinc chloride, zinc bromide, magnesium bromide, copper chloride, copper sulfate, and combinations thereof. In embodiments, the aggregating agent may be added to the mixture at a temperature that is below the glass transition temperature (Tg) of the resin.
The aggregating agent may be added to the mixture utilized to form a toner in an amount of, for example, from 0.1 % to 8% by weight, in embodiments from 0.2% to 5% by weight, in other embodiments from 0.5% to 5% by weight, of the resin in the mixture. This provides a sufficient amount of agent for aggregation.
In order to control aggregation and coalescence of the particles, in embodiments the aggregating agent may be metered into the mixture over time. For example, the agent may be metered into the mixture over a period of from 5 to 240 minutes, in embodiments from 30 to 200 minutes, although more or less time may be used as desired or required. The addition of the agent may also be done while the mixture is maintained under stirred conditions, in embodiments from 50 rpm to 1,000 rpm, in other embodiments from 100 rpm to 500 rpm, and at a temperature that is below the glass transition temperature of the resin as discussed above, in embodiments from 30 °C to 90 °C, in embodiments from 35°C to 70 °C.
The particles may be permitted to aggregate and/or coalesce until a predetermined desired particle size is obtained. A predetermined desired size refers to the desired particle size to be obtained as determined prior to formation, and the particle size being monitored during the growth process until such particle size is reached. Samples may be taken during the growth process and analyzed, for example with a Coulter Counter, for average particle size. The aggregation/coalescence thus may proceed by maintaining the elevated temperature, or slowly raising the temperature to, for example, from 40°C to 100°C, and holding the mixture at this temperature for a time from 0.5 hours to 6 hours, in embodiments from 1 to 5 hours, while maintaining stirring, to provide the aggregated particles. Once the predetermined desired particle size is reached, then the growth process is halted. In embodiments, the predetermined desired particle size is within the toner particle size ranges mentioned above.
The growth and shaping of the particles following addition of the aggregation agent may be accomplished under any suitable conditions. For example, the growth and shaping may be conducted under conditions in which aggregation occurs separate from coalescence. For separate aggregation and coalescence stages, the aggregation process may be conducted under shearing conditions at an elevated temperature, for example of from 40°C to 90°C, in embodiments from 45°C to 80°C, which may be below the glass transition temperature of the resin as discussed above.
Following aggregation to the desired particle size, the particles may then be coalesced to the desired final shape, the coalescence being achieved by, for example, heating the mixture to a temperature of from 65°C to 105°C, in embodiments from 70°C to 95°C, which may be at or above the glass transition temperature of the resin, and/or increasing the stirring, for example to from 400 rpm to 1,000 rpm, in embodiments from 500 rpm to 800 rpm. Higher or lower temperatures may be used, it being understood that the temperature is a function of the resins used for the binder. Coalescence may be accomplished over a period of from 0.1 to 9 hours, in embodiments from 0.5 to 4 hours.
After aggregation and/or coalescence, the mixture may be cooled to room temperature, such as from 20°C to 25°C. The cooling may be rapid or slow, as desired. A suitable cooling method may include introducing cold water to a jacket around the reactor. After cooling, the toner particles may be optionally washed with water, and then dried. Drying may be accomplished by any suitable method for drying including, for example, freeze-drying.

Shell resin

After aggregation, but prior to coalescence, a shell is applied to the aggregated particles.
In embodiments, the high molecular weight amorphous polyester resin used for forming the shell may have a polydispersity (M_wlM_n) of from 2 to 8, in embodiments from 3 to 6. While a narrow distribution of the molecular weight is often conventionally utilized, in embodiments of the present disclosure, a wide distribution of molecular weight may be utilized. In some embodiments, the high molecular weight amorphous polyester resin has a large polydispersity, for example at least 3, in embodiments at least 5. The large polydispersity may be utilized to ensure a low glass transition temperature (Tg) but a high viscosity of the amorphous polyester resin at a temperature of about 5°C higher than the Tg.
The high molecular weight resin utilized to form the shell comprises a poly(propoxylated bisphenol A co-fumarate) of the following formula:
wherein m is from 10 to 5000.
The high molecular weight amorphous polyester resin utilized in the shell has a glass transition temperature of from 40°C to 100°C, in embodiments from 50°C to 80°C, and a melt viscosity of from 50 to 1,000,000 Pa*S at 130°C, in embodiments from 100 to 100,000 Pa* at 130°C.
The high molecular weight amorphous polyester resin utilized in the shell has a softening point from 100°C to 200°C, in embodiments from 110°C to 150°C. The softening point of the high molecular weight amorphous polyester resin utilized in the shell may, in embodiments, be greater than 50°C higher than the coalescence temperature utilized in forming the toner particles, in embodiments from 50°C to 100°C higher than the coalescence temperature utilized in forming the toner particles.
The difference in softening point for a toner having a low molecular weight resin in its shell, compared with a toner having a high molecular weight resin in its shell, may be from 5°C to 100°C, in embodiments from 10°C to 50°C, depending upon the resins utilized.
The high molecular weight amorphous polyester resin utilized to form the shell may be utilized by itself or, in embodiments, the high molecular weight amorphous polyester resin may be combined with other amorphous resins to form a shell. The high molecular weight amorphous polyester resin may be present in an amount of from 20 percent by weight to 100 percent by weight of the total shell resin, in embodiments from 30 percent by weight to 90 percent by weight of the total shell resin. Thus, in embodiments, a second resin may be present in the shell resin in an amount of from 0 percent by weight to 80 percent by weight of the total shell resin, in embodiments from 10 percent by weight to 70 percent by weight of the shell resin.
In embodiments, the molecular weight of the high molecular weight amorphous polyester resin in the shell of a toner of the present disclosure may be at least 20% higher than the molecular weight of the amorphous resin in the core, in embodiments from 20% higher to 1000% higher than the molecular weight of the amorphous resin in the core, in embodiments from 50% higher to 500% higher than the molecular weight of the amorphous resin in the core.
The viscosity of the high molecular weight amorphous polyester resin in the shell of a toner of the present disclosure may be at least 50% higher than the viscosity of the amorphous resin in the core at about 130°C, in embodiments from 50% higher to 500% higher than the viscosity of the amorphous resin in the core at about 130°C, in embodiments from 80% higher to 200% higher than the viscosity of the amorphous resin in the core at about 130°C.
The shell thus formed using a high molecular weight amorphous resin may have a thickness of from 50 nm to 2 µm, in embodiments from 200 nm to 1 µm.
The shell resin may be applied to the aggregated particles by any method within the purview of those skilled in the art. In embodiments, the shell resin may be in an emulsion including any surfactant described above. The aggregated particles described above may be combined with said emulsion so that the high molecular weight amorphous polyester resin forms a shell over the formed aggregates.
Toner particles having a shell of the present disclosure may thus have a size of from 3 µm to 15 µm, in embodiments from 4 µm to 12 µm, and a glass transition temperature of from 30°C to 80°C, in embodiments from 35°C to 65°C.
Once the desired final size of the toner particles is achieved, the pH of the mixture may be adjusted with a base to a value of from 3 to 10, and in embodiments from 5 to 9. The adjustment of the pH may be utilized to freeze, that is to stop, toner growth. The base utilized to stop toner growth may include any suitable base such as, for example, alkali metal hydroxides such as, for example, sodium hydroxide, potassium hydroxide, ammonium hydroxide, and combinations thereof. In embodiments, ethylene diamine tetraacetic acid (EDTA) may be added to help adjust the pH to the desired values noted above.
The high molecular weight amorphous polyester resin utilized to form the shell may have a lower acid number compared with a lower molecular weight polyester resin. While a lower acid number usually corresponds to poor charging performance, it was surprisingly found that toners of the present disclosure with high molecular weight amorphous polyester resins in their shell and low acid numbers possessed excellent charging characteristics. The acid value of the resin utilized to form the core may be from 5 to 100 mL KOH/g polymer, in embodiments from 10 to 50 mL KOH/g polymer, while the acid value of the resin utilized to form the shell may be from 5 to 100 mL KOH/g polymer, in embodiments from 10 to 40 mL KOH/g polymer.
As the amorphous polyester resin utilized to form the shell has a higher molecular weight, which indicates a higher viscosity of the shell, the high molecular weight amorphous resin may be able to prevent any crystalline resin in the core from migrating to the toner surface. In addition, the high molecular weight amorphous polyester resin may be less compatible with the crystalline resin utilized in forming the core, which may result in a higher toner glass transition temperature (Tg), and thus improved blocking and charging characteristics may be obtained. Moreover, toners of the present disclosure having high molecular weight amorphous polyester resin in the shell may exhibit excellent document offset performance characteristics. While not wishing to be bound by any theory, it is believed the higher viscosity of the high molecular weight polyester resin in the shell may be responsible for imparting the above desired characteristics to the toner particles.

Additives

In embodiments, the toner particles may also contain other optional additives, as desired or required. For example, the toner may include positive or negative charge control agents, for example in an amount of from 0.1 to 10 percent by weight of the toner, in embodiments from 1 to 3 percent by weight of the toner. Examples of suitable charge control agents include quaternary ammonium compounds inclusive of alkyl pyridinium halides; bisulfates; alkyl pyridinium compounds, including those disclosed in U.S. Patent No. 4,298,672 ; organic sulfate and sulfonate compositions, including those disclosed in U.S. Patent No. 4,338,390 ; cetyl pyridinium tetrafluoroborates; distearyl dimethyl ammonium methyl sulfate; aluminum salts such as BONTRON E84™ or E88™ (Hodogaya Chemical); and combinations thereof. Such charge control agents may be applied simultaneously with the shell resin described above or after application of the shell resin.
There can also be blended with the toner particles external additive particles including flow aid additives, which additives may be present on the surface of the toner particles. Examples of these additives include metal oxides such as titanium oxide, silicon oxide, tin oxide, and mixtures thereof; colloidal and amorphous silicas, such as AEROSIL®, metal salts and metal salts of fatty acids inclusive of zinc stearate, aluminum oxides, cerium oxides, and mixtures thereof. Each of these external additives may be present in an amount of from 0.1 percent by weight to 5 percent by weight of the toner, in embodiments of from 0.25 percent by weight to 3 percent by weight of the toner. Suitable additives include those disclosed in U.S. Patent Nos. 3,590,000 , 3,800,588 , and 6,214,507 . Again, these additives may be applied simultaneously with the shell resin described above or after application of the shell resin.
In embodiments, toners of the present disclosure may be utilized as ultra low melt (ULM) toners. In embodiments, the dry toner particles, exclusive of external surface additives, may have the following characteristics:

(1) Volume average diameter (also referred to as "volume average particle diameter") of from 3 to 25 µm, in embodiments from 4 to 15 µm, in other embodiments from 5 to 12 µm.
(2) Number Average Geometric Size Distribution (GSDn) and/or Volume Average Geometric Size Distribution (GSDv) of from 1.05 to 1.55, in embodiments from 1.1 to 1.4.
(3) Circularity of from 0.9 to 0.99 (measured with, for example, a Sysmex FPIA 2100 analyzer).

The characteristics of the toner particles may be determined by any suitable technique and apparatus. Volume average particle diameter D_50v, GSDv, and GSDn may be measured by means of a measuring instrument such as a Beckman Coulter Multisizer 3, operated in accordance with the manufacturer's instructions. Representative sampling may occur as follows: a small amount of toner sample, about 1 gram, may be obtained and filtered through a 25 micrometer screen, then put in isotonic solution to obtain a concentration of about 10%, with the sample then run in a Beckman Coulter Multisizer 3.
Toners produced in accordance with the present disclosure may possess excellent charging characteristics when exposed to extreme relative humidity (RH) conditions. The low-humidity zone (C zone) is about 10°C/15% RH, while the high humidity zone (A zone) is about 28°C/85% RH. Toners of the present disclosure may also possess a parent toner charge per mass ratio (Q/M) of from -3 µC/g to -35 µC/g, and a final toner charging after surface additive blending of from -5 µC/g to -50 µC/g.
In accordance with the present disclosure, the charging of the toner particles may be enhanced, so less surface additives may be required, and the final toner charging may thus be higher to meet machine charging requirements.

Developers

The toner particles may be formulated into a developer composition. The toner particles may be mixed with carrier particles to achieve a two-component developer composition. The toner concentration in the developer may be from 1% to 25% by weight of the total weight of the developer, in embodiments from 2% to 15% by weight of the total weight of the developer.

Carriers

Examples of carrier particles that can be utilized for mixing with the toner include those particles that are capable of triboelectrically obtaining a charge of opposite polarity to that of the toner particles. Illustrative examples of suitable carrier particles include granular zircon, granular silicon, glass, steel, nickel, ferrites, iron ferrites, and silicon dioxide. Other carriers include those disclosed in U.S. Patent Nos. 3,847,604 , 4,937,166 , and 4,935,326 .
The selected carrier particles can be used with or without a coating. In embodiments, the carrier particles may include a core with a coating thereover which may be formed from a mixture of polymers that are not in close proximity thereto in the triboelectric series. The coating may include fluoropolymers, such as polyvinylidene fluoride resins, terpolymers of styrene, methyl methacrylate, and/or silanes, such as triethoxy silane, tetrafluoroethylenes, and other known coatings. For example, coatings containing polyvinylidenefluoride, available, for example, as KYNAR 301 F™, and/or polymethylmethacrylate, for example having a weight average molecular weight of 300,000 to 350,000, such as commercially available from Soken, may be used. In embodiments, polyvinylidenefluoride and polymethylmethacrylate (PMMA) may be mixed in proportions of from 30 to 70 weight % to 70 to 30 weight %, in embodiments from 40 to 60 weight % to 60 to 40 weight %. The coating may have a coating weight of, for example, from 0.1 to 5% by weight of the carrier, in embodiments from 0.5 to 2% by weight of the carrier.
In embodiments, PMMA may optionally be copolymerized with any desired comonomer, so long as the resulting copolymer retains a suitable particle size. Suitable comonomers can include monoalkyl, or dialkyl amines, such as a dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, diisopropylaminoethyl methacrylate, or t-butylaminoethyl methacrylate. The carrier particles may be prepared by mixing the carrier core with polymer in an amount from 0.05 to 10 percent by weight, in embodiments from 0.01 percent to 3 percent by weight, based on the weight of the coated carrier particles, until adherence thereof to the carrier core by mechanical impaction and/or electrostatic attraction.
Various effective suitable means can be used to apply the polymer to the surface of the carrier core particles, for example, cascade roll mixing, tumbling, milling, shaking, electrostatic powder cloud spraying, fluidized bed, electrostatic disc processing, electrostatic curtain, and combinations thereof. The mixture of carrier core particles and polymer may then be heated to enable the polymer to melt and fuse to the carrier core particles. The coated carrier particles may then be cooled and thereafter classified to a desired particle size.
In embodiments, suitable carriers may include a steel core, for example of from 25 to 100 µm in size, in embodiments from 50 to 75 µm size, coated with 0.5% to 10% by weight, in embodiments from 0.7% to 5% by weight, of a conductive polymer mixture including, for example, methylacrylate and carbon black using the process described in U.S. Patent Nos. 5,236,629 and 5,330,874 .
The carrier particles can be mixed with the toner particles in various suitable combinations. The concentrations are may be from 1% to 20% by weight of the toner composition. However, different toner and carrier percentages may be used to achieve a developer composition with desired characteristics.

Imaging

The toners can be utilized for electrophotographic or xerographic processes, including those disclosed in U.S. Patent No. 4,295,990 . In embodiments, any known type of image development system may be used in an image developing device, including, for example, magnetic brush development, jumping single-component development, and hybrid scavengeless development (HSD). These and similar development systems are within the purview of those skilled in the art.
Imaging processes include, for example, preparing an image with a xerographic device including a charging component, an imaging component, a photoconductive component, a developing component, a transfer component, and a fusing component. In embodiments, the development component may include a developer prepared by mixing a carrier with a toner composition described herein. The xerographic device may include a high speed printer, a black and white high speed printer, or a color printer.
Once the image is formed with toners/developers via a suitable image development method such as any one of the aforementioned methods, the image may then be transferred to an image receiving medium such as paper. In embodiments, the toners may be used in developing an image in an image-developing device utilizing a fuser roll member. Fuser roll members are contact fusing devices that are within the purview of those skilled in the art, in which heat and pressure from the roll may be used to fuse the toner to the image-receiving medium. In embodiments, the fuser member may be heated to a temperature above the fusing temperature of the toner, for example to temperatures of from 70°C to 160°C, in embodiments from 80°C to 150°C, in other embodiments from 90°C to 140°C, after or during melting onto the image receiving substrate.
In embodiments where the toner resin is crosslinkable, such crosslinking may be accomplished in any suitable manner. For example, the toner resin may be crosslinked during fusing of the toner to the substrate where the toner resin is crosslinkable at the fusing temperature. Crosslinking also may be effected by heating the fused image to a temperature at which the toner resin will be crosslinked, for example in a post-fusing operation. In embodiments, crosslinking may be effected at temperatures of from 160°C or less, in embodiments from 70°C to 160°C, in other embodiments from 80°C to 140°C.
The following Examples are being submitted to illustrate embodiments of the present disclosure. Parts and percentages are by weight unless otherwise indicated. As used herein, "room temperature" refers to a temperature of from 20 ° C to 25° C.

COMPARATIVE EXAMPLE 1

About 397.99 grams of a linear amorphous resin in an emulsion (about 17.03 weight % resin) was added to a 2 liter beaker. The linear amorphous resin was of the following formula:
wherein m was from 5 to 1000 synthesized following the procedures described in U.S. Patent No. 6,063,827 . About 74.27 grams of an unsaturated crystalline polyester ("UCPE") resin composed of ethylene glycol and a mixture of dodecanedioic acid and fumaric acid co-monomers with the following formula:
wherein b is from 5 to 2000 and d is from 5 to 2000 in an emulsion (about 19.98 weight % resin), synthesized following the procedures described in U.S. Patent Application Publication No. 2006/0222991 , and about 29.24 grams of a cyan pigment, Pigment Blue 15:3, (about 17 weight %) was added to the beaker. About 36 grams of Al₂(SO₄)₃ (about 1 weight %) was added as flocculent under homogenization by mixing the mixture at 3000 to 4000 rpm.
The mixture was subsequently transferred to a 2 liter Buchi reactor, and heated to about 45.9° C for aggregation and mixed at a speed of about 750 rpm. The particle size was monitored with a Coulter Counter until the size of the particles reached an average volume particle size of about 6.83 µm with a Geometric Size Distribution ("GSD") of about 1.21. About 198.29 grams of the above emulsion with the resin of formula I was then added to the particles to form a shell thereover, resulting in particles possessing a core/shell structure with an average particle size of about 8.33 µm, and a GSD of about 1.21.
Thereafter, the pH of the reaction slurry was increased to about 6.7 by adding NaOH followed by the addition of about 0.45 pph EDTA (based on dry toner) to freeze, that is stop, the toner growth. After stopping the toner growth, the reaction mixture was heated to about 69° C and kept at that temperature for about 1 hour for coalescence.
The resulting toner particles had a final average volume particle size of about 8.07, and a GSD of about 1.22.
The toner slurry was then cooled to room temperature, separated by sieving (utilizing a 25 µm sieve) and filtered, followed by washing and freeze drying.

EXAMPLE 1

About 397.99 grams of a linear amorphous resin in an emulsion (about 17.03 weight % resin) was added to a 2 liter beaker. The linear amorphous resin was of the following formula:
wherein m was from 5 to 1000. About 74.27 grams of the unsaturated CPE resin emulsion (formula IV) from Comparative Example 1 above (about 19.98 weight % resin), and about 29.24 grams of cyan pigment, Pigment Blue 15:3, (about 17 weight %) were added to the beaker. About 36 grams Al₂(SO₄)₃ (about 1 weight %) was added as a flocculent under homogenization by mixing the mixture at 3000 to 4000 rpm.
The mixture was subsequently transferred to a 2 liter Buchi reactor, and heated to about 45.5° C, for aggregation with mixing at about 750 rpm. The particle size was monitored with a Coulter Counter until the size of the particles reached an average volume particle size of about 6.97 µm with a GSD of about 1.25.
About 149.48 grams of a high molecular weight amorphous resin having the same formula as the resin utilized as the core (formula I) in an emulsion (about 22.59 weight % resin) was added as shell.

Summaries of the differences between the low molecular weight amorphous resin utilized in the shell of Comparative Example 1 and the high molecular weight amorphous resin utilized in the shell of Example 1 are summarized below in Table 1; differences in the rheological properties of toners produced with the low molecular weight amorphous resin utilized in the shell of Comparative Example 1 and the high molecular weight amorphous resin utilized in the shell of Example 1 are summarized in the Figure.

Table 1

Amorphous Resin in Shell	Mw	Mn	Acid Value (mL KOH/g polymer)	Softening Point °C	Tg onset °C
Low Mw resin (Comparative Example 1)	12.5	4.4	16.7	107	56.7
High Mw resin (Example 1)	38.8	6.4	12	123	62

The acid number was determined to verify the presence of acid moieties and was determined by titrating the acid groups. The acid number was the number of milligrams of potassium hydroxide necessary to neutralize the free acids in 1 gram of resin.
The high molecular weight amorphous resin formed a shell over the core particles produced above, resulting in particles possessing a core/shell structure with an average volume particle size of about 8.15 µm, and a GSD of about 1.23.
Thereafter, the pH of the reaction slurry was increased to about 6.1 by adding NaOH followed by the addition of about 0.45 pph EDTA (based on dry toner) to freeze, that is stop, the toner growth. After stopping the growth of the toner particles, the reaction mixture was heated to about 69° C and kept at that temperature for about 7 hours for coalescence.
The resulting toner particles had a final average volume particle size of about 8.07 µm, and a GSD of about 1.25.
The toner slurry was then cooled to room temperature, separated by sieving (utilizing a 25 µm sieve) and filtered, followed by washing and freeze drying.
Compared to the toner having a lower molecular weight amorphous resin in the shell as produced in Comparative Example 1, the toner with a high molecular weight amorphous resin in the shell as produced in Example 1 showed a significant improvement in both A-zone and C-zone charging, as measured by a total blow off apparatus also known as Barbetta box. Developers were conditioned overnight in A and C zones and then charged using a paint shaker for from 5 to 60 minutes to provide information about developer stability with time and between zones. The toner or Example 1 with the high molecular weight resin in the shell also showed improved relative humidity sensitivity, while maintaining the same morphology as the toner produced in Comparative Example 1 with the lower molecular weight resin in the shell. Summaries of the data obtained for the low molecular weight amorphous resin utilized in the shell of Comparative Example 1 and the high molecular weight amorphous resin utilized in the shell of Example 1 are summarized below in Table 2. Table 2

Sample Parent charging

Q/M AZ Q/M AZ Q/MCZ Q/M CZ

5M-PS 60M-PS 5M-PS 60M-PS

Comparative Example 1 -3.7 -3.6 -16.6 -13.7

Example 1 -6.02 -10.31 -24.5 -27.5

Q/M = charge per mass ratio
AZ = A-zone 28 °C/85%RH
CZ = C-zone 10 °C/15%RH
5M-PS = Short developer charging time of 5 minutes
60M-PS= Longer developer charging time of 60 minutes
Fusing characteristics of the toners produced in Comparative Example 1 and Example 1 were also determined by crease area, minimum fixing temperature, gloss, document offset, and vinyl offset testing.

Crease Area

The toner image displays mechanical properties such as crease, as determined by creasing a section of the substrate such as paper with a toned image thereon and quantifying the degree to which the toner in the crease separates from the paper. A good crease resistance may be considered a value of less than 1 mm, where the average width of the creased image is measured by printing an image on paper, followed by (a) folding inwards the printed area of the image, (b) passing over the folded image a standard TEFLON coated copper roll weighing about 860 grams, (c) unfolding the paper and wiping the loose ink from the creased imaged surface with a cotton swab, and (d) measuring the average width of the ink free creased area with an image analyzer. The crease value can also be reported in terms of area, especially when the image is sufficiently hard to break unevenly on creasing; measured in terms of area, crease values of 100 millimeters correspond to about 1 mm in width. Further, the images exhibit fracture coefficients, for example of greater than unity. From the image analysis of the creased area, it is possible to determine whether the image shows a small single crack line or is more brittle and easily cracked. A single crack line in the creased area provides a fracture coefficient of unity while a highly cracked crease exhibits a fracture coefficient of greater than unity. The greater the cracking, the greater the fracture coefficient. Toners exhibiting acceptable mechanical properties, which are suitable for office documents, may be obtained by utilizing the aforementioned thermoplastic resins. However, there is also a need for digital xerographic applications for flexible packaging on various substrates. For flexible packaging applications, the toner materials must meet very demanding requirements such as being able to withstand the high temperature conditions to which they are exposed in the packaging process and enabling hot pressure-resistance of the images. Other applications, such as books and manuals, require that the image does not document offset onto the adjacent image. These additional requirements require alternate resin systems, for example that provide thermoset properties such that a crosslinked resin results after fusing or post-fusing on the toner image.

Minimum Fixing Temperature

The Minimum Fixing Temperature (MFT) measurement involves folding an image on paper fused at a specific temperature, and rolling a standard weight across the fold. The print can also be folded using a commercially available folder such as the Duplo D-590 paper folder. The folded image is then unfolded and analyzed under the microscope and assessed a numerical grade based on the amount of crease showing in the fold. This procedure is repeated at various temperatures until the minimum fusing temperature (showing very little crease) is obtained.

Gloss

Print gloss (Gardner gloss units or "ggu") was measured using a 75° BYK Gardner gloss meter for toner images that had been fused at a fuser roll temperature range of 120°C to 210°C (sample gloss was dependent on the toner, the toner mass per unit area, the paper substrate, the fuser roll, and fuser roll temperature).

Document Offset

A standard document offset mapping procedure was performed as follows. Five centimeter (cm) by five cm test samples were cut from the prints taking care that when the sheets are placed face to face, they provide both toner to toner and toner to paper contact. A sandwich of toner to toner and toner to paper was placed on a clean glass plate. A glass slide was placed on the top of the samples and then a weight comprising a 2000 gram mass was placed on top of the glass slide. The glass plate was then inserted into an environmental chamber at a temperature of 60°C where the relative humidity was kept constant at 50%. After 7 days, the samples were removed from the chamber and allowed to cool to room temperature before the weight was removed. The removed samples were then carefully peeled apart. The peeled samples were mounted onto a sample sheet and then visually rated with a Document Offset Grade from 5.0 to 1.0, wherein a lower grade indicates progressively more toner offset, ranging from none (5.0) to severe (1.0). Grade 5.0 indicates no toner offset and no adhesion of one sheet to the other. Grade 4.5 indicates noticeable adhesion, but no toner offset. Grade 4 indicates that a very small amount of toner offsets to the other sheet. Grade 3 indicates that less than 1/3 of the toner image offsets to the other sheet, while Grade 1.0 indicates that more than 1/2 of the toner image offsets to the other sheet. In general, an evaluation of greater than or equal to 3.0 is considered the minimum acceptable offset, and an evaluation of greater than or equal to 4.0 is desirable.

Vinyl Offset

Vinyl offset was evaluated as follows. Toner images were covered with a piece of standard vinyl (32% dioctyl phthalate Plasticizer), placed between glass plates, loaded with a 250 gram weight, and placed in an environmental oven at a pressure of 10 g/cm², 50°C and 50% relative humidity (RH). After about 24 hours, the samples were removed from the oven and allowed to cool to room temperature. The vinyl and toner image were carefully peeled apart, and evaluated with reference to a vinyl offset evaluation rating procedure as described above for document offset wherein Grades 5.0 to 1.0 indicate progressively higher amounts of toner offset onto the vinyl, from none (5.0) to severe (1.0). Grade 5.0 indicates no visible toner offset onto the vinyl and no disruption of the image gloss. Grade 4.5 indicates no toner offset, but some disruption of image gloss. An evaluation of greater than or equal to 4.0 is considered an acceptable grade.

The results obtained for the toners of Comparative Example 1 and Example I are summarized below in Table 3.

Table 3

	Goal	Comparative Example 1	Example 1
DCX+ (90 gsm) paper
Cold Offset°C		113	130
Hot Offset°C		>210	>210
T_G40	5175°C	142	159
Gloss @ MFT	40 ggu	38.0	28.6
Gross @ 185°C	≥ 40	72.5	63.3
Peak Gloss	≥ 50	72.6	66.6
MFT_CA=85	≤ 169°C	140	148
AMFT_CA=85		-34	-22
MFT/ΔMFT	Gloss 40 & CA=85	142/-34	159/-20
FC_CA=85		4.34	4.29
Document Offset (Toner-Toner) SIR (rmsLA)	≥ iGen3 Ideally 4	1.00 (15.1)	2.00 (0.23)
Document Offset (Toner-Paper) SIR (% toner)	≥ iGen3 Ideally 4	1.00 (12.5)	1.75 (0.92)
Vinyl Offset SIR (% toner)	≥ 4 FX vinyl	N/A	N/A

DCEG (120 gsm) Paper
T_C40	≤175°C	141	155
Gloss @ MFT	40 ggu	31.5	33.6
Gloss @ 185°C	≥ 40	80.2	80.0
Peak Gloss	≥ 50	94.1	92.5
MFT_CA=85	≤ 169°C	137	151
ΔMFT_CA=85		-34	-23

MFT=Minimum fixing temperature (minimum temperature at which acceptable adhesion of the toner to the support medium occurs)
DCX =Uncoated Xerox paper
DCEG =Coated Xerox paper
gsm = grams per square meter
CA =crease area
T_G40 =Fusing temperature to reach 40 gloss unit

As can be seen from Table 3, using a high molecular weight amorphous resin as the shell layer improved the 24-hour document offset properties of the toner. Severe toner to toner (15.1 grams) and toner to paper (12.5 grams) damage was visible for the toner of Comparative Example 1, SIR = 1.00/1.25. To the contrary, the toner of Example 1 with the high molecular weigh amorphous resin in the shell was ranked SIR = 2.00 (toner to toner, 0.23 grams) and SIR = 1.75 (toner to paper, 0.92 grams).
Using a high molecular weight amorphous resin in the shell also shifted the Crease fix MFT _CA=85 to a higher temperature: the temperature went from about 140°C (Comparative Example 1) to about 148°C (Example 1) on uncoated paper core, and a similar trend was observed on coated paper.

Claims

A toner composition comprising toner particles comprising:
a core comprising at least one crystalline resin, and one or more optional ingredients selected from the group consisting of colorants, optional waxes, and combinations thereof; and

a shell comprising a high molecular weight amorphous polyester resin having a weight average molecular weight of from 20,000 to 1,000,000, as determined by Gel Permeation Chromatography using polystyrene standards,

wherein the high molecular weight amorphous polyester resin comprises a poly(propoxylated bisphenol A co-fumarate) of the following formula:
wherein m is from 10 to 5000, and wherein the high molecular weight amorphous polyester resin is present in an amount of from 20 to 100 percent by weight of the shell resin, has a glass transition temperature of from 40 to 100°C, a softening point of from 100 to 200°C, and a melt viscosity of from 50 to 1,000,000 Pa·s at 130°C.
A toner composition according to claim 1, wherein the core further comprises an amorphous resin.
A toner composition according to claim 1, wherein the crystalline resin is selected from the group consisting of polyesters, polyamides, polyimides, polyolefins, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, and combinations thereof.
A toner composition according to claim 1, wherein the core further comprises an amorphous resin selected from the group consisting of polyesters, poly(styrene-acrylate) resins, crosslinked poly(styrene-acrylate) resins, poly(styrene-methacrylate) resins, crosslinked poly(styrene-methacrylate) resins, poly(styrene-butadiene) resins, crosslinked poly(styrene-butadiene) resins, alkali sulfonated-polyester resins, alkali sulfonated-polyimide resins, alkali sulfonated-polyimide resins, alkali sulfonated poly(styrene-acrylate) resins, crosslinked alkali sulfonated poly(styrene-acrylate) resins, poly(styrene-methacrylate) resins, crosslinked alkali sulfonated-poly(styrene-methacrylate) resins, alkali sulfonated-poly(styrene-butadiene) resins, crosslinked alkali sulfonated poly(styrene-butadiene) resins, and combinations thereof.
A toner composition according to claim 1, wherein the core further comprises a poly(propoxylated bisphenol A co-fumarate) resin of the formula:
wherein m is from 5 to 1000.
A toner composition according to claim 2, wherein the molecular weight of the amorphous polyester resin in the shell is at least 20% higher than the molecular weight of the amorphous resin in the core, the viscosity of the amorphous polyester resin in the shell is at least 50% higher than the viscosity of the amorphous resin in the core at 130°C, and wherein the shell has a thickness from 50 nm to 2 µm.
A toner composition according to claim 1, wherein the core comprises at least one amorphous resin and at least one polyester crystalline resin.
A toner composition according to claim 1, wherein the shell further comprises a second resin present in an amount of from 10 to 70 percent by weight of the shell, and the high molecular weight resin is present in an amount of from 30 to 90 percent by weight of the shell.
A toner composition according to claim 1, wherein the shell has a thickness of from 50 nm to 2 µm.
A toner composition according to claim 1, wherein the core further comprises at least one amorphous resin; and
the shell resin comprises the high molecular weight amorphous polyester resin in combination with a second polyester resin of the formula:
wherein b is from 5 to 2000, and d is from 5 to 2000, and
wherein the high molecular weight amorphous polyester resin is present in an amount of from 30 to 90 percent by weight of the shell, and the second resin is present in an amount of from 10 to 70 percent by weight of the shell.